Isolation and Properties of Spore Germination Mutants of Bacillus subtilis 168 Deficient in the Initiation of Germination

Two spore germination mutants of Bacillus subtilis 168 (GerA38 and GerA44) deficient at a very early stage of germination prior to loss of heat resistance and absorbance were isolated. In contrast to the wild-type their spores required higher concentrations of germinant and had a slower germination rate and longer average microlag in l-alanine, l-α-aminobutyrate, dl-β-aminobutyrate and l-valine. Although wild-type spores germinated in 0·1 m-CyCloleucine the mutants did not, but did so normally in l-asparagine plus glucose, fructose and KCl. GerA44 was more defective than GerA38. Their germination abnormalities were partially corrected if glucose, fructose and KCl were added to l-alanine or l-valine. Germination of both mutants in l-alanine was more sensitive than the wild-type to inhibition by d-alanine, the sensitivity of GerA44 being greater than that of GerA38. Two other GerA mutants which did not germinate in L-alanine, even at high concentrations, were able to use it as a source of carbon or nitrogen at rates equal to those of the wild-type. A similar mutant and GerA44 show normal chemotaxis to l-alanine. Thus, the deficiencies of GerA mutants appear to be spore specific. GerA38 and gerA44 mutations were approximately 75% and 43% cotransduced with cysB and thr-5, respectively, with phage PBS1. They mapped within a cluster of gerA mutations that were 70–90% cotransduced with citG4 by phage SPP1. Although other GerA mutants cannot germinate in l-alanine plus KCl no difference in map location between their mutations and gerA38 and gerA44 could be detected.